In known camera systems, a strip of light sensitive emulsion, film, is typically wound onto a spool and enclosed in a light tight cartridge. This film cartridge is inserted into an exposing system of the camera to capture images. The film to be exposed is typically wound out of the cartridge, exposed, and wound onto a take-up spool. During camera operation, the film is moved incrementally from the cartridge to the take-up spool and exposures are made onto a series of light sensitized areas on the film. At the end of the exposure sequence, the film is wound back into the cartridge and removed from the camera.
It is advantageous to track the number of exposures that have been made for a given cartridge. In known 35 mm format systems, a sprocket meters 8 perforations on a film and increments a counter system. These counter systems are typically viewed from the top of the camera and are harder to read than a counter on the back of a camera. The Keystone "LeClic/Easy Shot 400" counts frames on the back of the camera using a worm gear to rotate a spring loaded counter wheel. Opening a film door on the camera releases the worm gear from the counter wheel, and the counter returns to a home position.
In other camera systems, the series of perforations on the film are eliminated or the perforations are used only to delimit each frame. Thus a film counter cannot use sprockets engaging the perforations to count frames of film. In simple mechanical cameras that use delimiting perforations, metering mechanisms typically mechanically inhibit the shutter release button and prevent film advance until the next frame has been advanced into the exposure area of the camera. It is advantageous to implement frame counting from the metering/shuttering actuation. It is also advantageous to display the frame count on the back of the camera.